The aim of this study is to determine Lepidoptera fauna of the Yuvacik Dam Watershed in Kocaeli. The
study was conducted in 2007 from March to November. 493 specimens were collected from study area.
A total of 119 species belonging to 16 families of Lepidoptera order were identified. Polyommatus
dorylas [(Den and Schiff, 1775) and Zerynthia cerisy (Godart, 1822)] are considered as Near Threatened
(NT) category according to IUCN Butterflies Red List Criteria.
Key words: Lepidoptera, Yuvacik, Kocaelis, species, fauna.